This proposal describes a 5-year training program to enable the applicant to expand her scientific knowledge, advance her technical skills, and establish independence from her primary mentor. In addition to her primary mentor, the applicant has a co-mentor to help supervise the applicant's scientific progress and progress toward independence. In addition, an Advisory Committee, meeting twice yearly, will oversee her work and career development. The overall scientific objectives are to determine the mechanisms of interaction between Thymic Stromal Lymphopoietin (TSLP) and Transforming Growth Factor Beta (TGFB) in vitro and in vivo. TSLP had previously been implicated in Th2 skewing and IL-13 production. My recent data show that chronic administration of TSLP subcutaneously also regulates profibrotic genes, highly overlapping those regulated by TGFB. In addition, in other experiments, I found that the effect of chronic subcutaneous administration of TGFB is blocked in mice deleted of TSLP, tightly linking these two cytokines. Investigating the possible role for TSLP in systemic sclerosis, I found that perivascular macrophages stain strongly with this cytokine, suggesting that TSLP also strongly contributes to systemic sclerosis (SSc) skin disease. Therefore, I hypothesize that TSLP contributes to the development of fibrosis in SSc through interactions with TGFB that include overlapping downstream signaling, and a requirement for TSLP in the profibrotic activity of TGFB. To test this hypothesis, the first aim will examine the effect of TSLP and TGFB on profibrotic gene expression by fibroblasts, studying known TSLP and TGFB signaling pathways. This aim will also examine the effect of TSLP in several murine fibrotic models, including the effect of TSLP deletion on bleomycin- and TGFB-induced lung fibrosis models. In addition this aim will test the effect of a TSLP signaling inhibitor, tofacitinib, recently approved for rheumatoid arthritis, in these models. The second aim will further investigate the significance of these murine studies in human SSc, by characterizing a TSLP-gene signature, by identifying the expression of TSLP-signature genes in SSc skin, and by evaluating whether this signature changes in samples from a trial of anti- TGFB in SSc patients. Understanding the role of TSLP in murine models and SSc skin and lung fibrosis will enhance our understanding not only of the SSc pathogenesis, but also of the fibrosis more generally. Immediate and Long-term career goals. My career goal is to lead an academic research group focused on understanding the basic pathogenic mechanisms involved in the development of systemic sclerosis (SSc). My ultimate objective is that the information obtained from my research will be applied to advance the discovery of safer and more effective therapies for systemic sclerosis, and/or used to develop biomarkers that can predict severe clinical complications, such as lung fibrosis, currently the main cause of mortality in these patients. Research Career Development The research proposed will provide me with opportunities to learn new technical skills involving in vivo murine models of skin disease, utilizing samples from ongoing biomarker studies to develop TSLP biomarkers, interpretation of in vitro and in vivo data and using murine models of ILD. In learning these practices with the guidance of my mentors and collaborators, I will acquire theoretical knowledge of the proposed topics. It will also be important for me to expand and broaden my knowledge of immunology and animal model analysis by keeping up to date on research, attending seminars and meetings at BUMC and elsewhere and taking two courses offered at BUMC: Comprehensive Immunology and Biochemistry and Cell Biology. Another important component of my training will be to advance my ability to present and discuss my data orally. This will be done in two ways: through participation in the weekly meeting in Dr. Lafyatis' laboratory where I will present my data on a regular basis and will be subjected to rigorous analysis and criticism. In addition, I will submit y work for presentation at national meetings, where I will also have the opportunity to exchange ideas and foster potential new collaborations with other scientists.